Rear-view mirror arrangements for motor vehicles have a reflective surface which affords a view of the following traffic. Commonly, rear-view mirror arrangements are additionally designed to be dimmable. In this way, during travel in darkness, glare from vehicles travelling behind is prevented. In the case of automatically dimmable rear-view mirror arrangements, light sensors measure or detect the difference in brightness between the area in front of the vehicle and the traffic area behind. The measurement values are then transmitted to evaluation and control electronics, and the reflective capability of the mirror arrangement is correspondingly changed. In this case, mirror assemblies are used which comprise optical cells. Said optical cells may for example be in the form of liquid-crystal cells. In the case of such mirror arrangements, the reflective capability can be changed through the application of an electric field.
Furthermore, rear-view mirror arrangements for the exterior region are commonly designed to be heatable. In this way, an impairment of the view by water droplets, frost and ice, in particular in winter months, is prevented. Here, conventional mirror arrangements which are not equipped with an optical cell comprise a glass plate, a reflective coating, and an areal heating element arranged on the rear side of the reflective coating. Said areal heating element is commonly a carrier foil which comprises an electric heating resistor and which is adhesively bonded to the reflective coating. In this case, the areal heating element is arranged on a carrier plate which bears the mirror assembly. The heat generated by the resistance element is in this case conducted through the reflective coating to the outwardly pointing glass plate, in order, for example, to effect de-icing of the outer surface there.
For a mirror assembly which comprises a liquid-crystal cell, the known areal heating elements described in the introduction, and the arrangement thereof, are however unsuitable. Adhesive bonding between carrier plate, areal heating element, liquid-crystal cell and glass plate leads to distortion owing to the tolerances of the individual parts within the liquid-crystal cell. Said distortions lead to accumulations of liquid crystals of the liquid-crystal medium in the liquid-crystal cell, leading to noticeable dark blemishes in the optical image that is visible to the user.
A heatable mirror assembly which comprises an optical cell is known from U.S. Patent Publication No. 2004/0240029 A1. In the case of said already known mirror assembly, the optical cell is connected by way of a medium to a reflector. In one design variant, provision is made for the reflector to be in the form of a heater. A further design variant provides for a heatable air gap to be provided between the optical cell and reflector.